Mercury switches



NOV- 3, 1959 w. G. GusTAFsoN ETAL 2,911,500

MERCURY SWITCHES OriginalA Filed Feb. 18, 1955 3 Sheets-Sheet l w. c.GUSTAFSON WVU/Tof"S H. c. HAM/50N BW C. MW

ATTORNEV Nov. 3, 1959 w. G. GusTAFsoN ET'AL MERCURY SWITCHES originalFiled Feb. 18, 1955 3 Sheets-Sheet 2 w. c. GUSTA/"50N NVENTS H. c.HAM/50N rem C.

ATTORNEY Nov. 3, 1959 w. G. GUs'rAFsoN ET AL 2,911,500

MERCURY SWITCHES 3 Sheets-Sheet 5 Original Filed Feb. 18, 1955 W G.GUSTFSON H. C. HARP/SON /NVENTORS ATTORNEY United States Patent OfficePatented Nov. 3, 1959 2,911,500 MERCURY SWITCHES 5 f Walter G.Gustafson, New York, and Henry C. Harrison,

Port Washington, N.Y., assignors to Bell Telephone Laboratories,Incorporated, New York, N.Y;, a corporation 4of New York Originalapplication February 18, 19'55, Serial No. 489,046, now PatentN0..2,837,612, dated June 3, 1958.

' Divided and this application October 16, 1957, Serial achim. (c1.zoo-112) This invention relates to circuit controlling devices and moreparticularly to such devices ofthe type commonly referred to as mercuryswitches. 'This application is a division of application vSerial No.489,046, led February 18, 1955, by Walter G. Gustafson and Henry C.Harri- `son (now Patent No. 2,837,612, dated June 3, 1958) in whichapplication are claimed certain features of a mercury contact switch.

Mercury switches comprise, in general, a pair of contacts and a body ofmercury, one or both of the contacts or the mercury. being movable toestablish a conductive path through these three elements or, conversely,to open such path. Heretofore, primarily because of the uid character ofmercury at the temperatures at which the switches usually are utilized,i-t was necessary that the switches be mounted or operated inaparticular position. Also, in such devices of the class wherein one orboth of the contacts lare movable to effect closure or opening of theconductive path or circuit, relatively large power eX- penditure hasbeen required to effect operation. Further, in devicesl of this class,chatter uopn making or breaking has been a problem. In addition, andthishas L been of special moment in cases where the switches have .powerrequisite for operation of such switches, to mini- Amizechatter and toreducethe' voltages developed in circuits including an inductive load,upon opening of 'the circuit.

Additional objects of this invention are to facilitate the fabricationof such switches, to simplify the structure thereof and to reduce thesize of' circuit controlling devices .capable of performing multiplefunctions, for example, make and break of .plural circuits` or transfer.

In one illustrative embodiment of this invention, a

circuit controlling device comprises a'fpair of terminals,

a body of mercury coupled to. one ofthe terminals and an armatureconnected to the other terminal and actuable to engage with or disengagefrom the mercury body.

VIn accordance with one `featureof this invention, the

mercury body is confined or localized within a container having thereinan aperture through which a contact attached to the armaturemay pass,the container being `constructed and Varranged 'so that irrespective ofthe position of the' device the mercury remains in operative rela tionwith respect'to the contact.

More specifically, in Iaccordance. with this'feature of the invention,the inner wall of the housing includes a portion opposite the contact,which is wet readily by 'mercury, kand the remaining portions are of amaterial which d oes not wet'` readily. In effect, the mercury adheresto; the readily wettable portion and is not displaceable easily byjarring or even inversion of the container.

In `accordance with another feature of this invention, theaforementioned wettable portion has thereadjacent an annular memberadapted to accommodate theA contact and defining a restricted passagewaywithin the container. The Contact, upon actuation to engage the mercury,forces some of the latter through the passageway, whereby a resistivedamping of the armature-contact motion is realized.

In accordance with still another feature of thisinvention, vibrationalenergy dissipative elements are provided for engaging the armature whenit operates to disengage the contact from the mercury.

In accordan'ce'with a further feature of this invention, the armatureand container are mounted respectively by a pair of substantiallyparallel magnetic members, the varmature being positioned between thetwo members and having one end lixed to onemember and its other endfree. Actuation of the armature is effected, for example by a signalcoil encompassing both the members, by mag-- netization of the memberssuch that one attracts and the other repels the' armature, whereby highsensitivity is real-ized.

In accordance with a still further feature of this invention, thecontact and container are correlated toy provide a small and constantgap 'therebetween fduring actuation ofthe contact, whereby the voltageinduced with an inductive load in the circuit being controlled isminimized.

In accordance with another featureof this invention, thecontactcomprises a portion readily wet by mercury,

' extending froma body which is not readily wet, the ex- 'comitantly orto effect transferbetween` circuits.

tending portion beingat the'end toward the body of mercury. Thus, atleast after a single operatiomwhereby theextending portionis wetbymercury, on a make the initial contact is between mercury and mercury,and

hence a quick and low resistanceclosure is attained. Be

cause of the non-wetting character of the contact body, substantialresistance to immersion of the'contact is developed. Hence, a stop isprovided upon motion of the con-tact. Further, because of thenon-wettingcharactervisftic noted, the force necessary to produce afbreak, i.e.,

to disengage the contact from the'mercury, is small.'

Theinvention may be embodied in switches for performing a variety ofdifferent functions, such as to make or break circuits, tocontrol aplurality of circuits con- Further, one or morernagnets may be'associated with the armature lactuating system to provide polarizedoperation',o r the armature may be operated by electrostatic means. i' vThe inventionand the features thereof will be understood more clearlyand fully from the following detailed description withreference to theaccompanying drawings, in which:

. j Fig. 1 is a longitudinal view of a mercury switch with the envelopebroken away to illustrate one `embodiment of the invention; 1 Fig. 2 isa sectional ViewV taken along the line 2 2 of the switch in Fig. 1;

Fig.' y3 is an exploded perspective view showing the asi sembly of arcontainer for the body of mercury;

, rainer when the 'switch is'fullyclosedg.

Fig. 4 yis a cross sectioned view of the mercury-.container when theswitch is in a fully open position; f

Fig. `5 iis a cross-.sectioned view of the mercury con- Figs. 6' .andicomprise-longitudinaiviews of two mdiaway; j l

Fig. 8V is a longitudinalrviewof another modification 70.* lcationsofthe device with the envelopes thereof broken .made of vitreousmaterial such as glass.

of the device with the armature in a normally closed position; p

Fig. 9 is a perspectiveview of a transfer switch embodying the featuresof the invention; and s Fig. 10 is an enlarged side view of the tubularelectrode shown in Fig. 9, illustrating'the means used to support thearmature. v

Referring to Fig. 1 of the drawings, there is shown a .preferredembodiment'of the invention. The elements of the mercury switch areenclosed in an` envelope 11 In order to suppress contact arcing, theenvelope maybe filled with laninert gas such as hydrogen, although thisis not yessential for operation of the switch. Inserted in the envelope11 are two electrodes 12 and 13 which comprise the contact terminals.These electrodes may be formed of any suitable material of highelectrical conductivity, but

inasmuch -as the switch is operated byl an external magnetic force it isimportant that the electrodes be made of magnetic material. `In thespecific embodiment shown `in Fig. l, the electrode 12 is tubular inshape, thereby facilitating fabrication since both the mercury and theinert gasmay be .inserted into the envelope through this tube.

Attached to the bottom of the electrode 12 is a sup- .porting member 14which is used to hold the armature 15 in place. These elements may lbespot welded together so that a continuous current carrying path isformed from the armature 15 to the electrode 12. To insure maximumoperating eiciency, the armature should not extend beyond the end of theelectrode. It is preferred to make the armature from aL thin permalloyreed so that maximum sensitivity maybe attained. The amature is biasedupward so that in its normal position it rests against the dampingspring 16 in such amanner that during contact breaks the deleteriouselfects of chatter arejreduced to a minimum. The damping spring 16 ismade of a'highly resilient material and is spot welded to the electrode12 so that the vibration ofthe armature 15 is reduced as much aspossible. t

Attached to the amature 15 is a contact pin 17, which l `is illustratedin detail in Figs. 4 and-5. The `pin is formed of a material notwettable bymercury and has a currentcarrying shaft 18 along its axisthat is mercury wettable and slightly longer than the contact pin 17, sothat it protr-udesv from the vbottom of the pin. This configuration hasseveral advantages. The mercury-Wettable shaft 18 retains a thin lm ofmercury-thereon which provides a mercury to mercury contact when thearmature 15 is energized, whereby a'quickand low resistance closure isattained. vBy makingthe contactpin 17 non-wettable, upon closure, thenatural resistance of the contact pin to immersion in mercury preventsthe shaft 18 from striking the bottom of the-mercury container 19, thusavoiding all solid contact and greatly increasing the life of theswitch. Furthermore, when the contact pin disengages there is verylittlesurface tension tending to hold it immersed inthe mercury, andconsequently theV sensitivity is greatly increased. A convenient methodof fabricat- `ring the contact pin 17 is to `cut it from a chromiumplated tungsten wire. The chromium platingshouldbe suiciently thick toprovide a large cross sectional area ratio between the contact pin 17and the shaft- V18, so 'that the above advantages may be fully realized.The chromium is etched until lthe tungsten protrudes from the lower endof the contact pin.l Since tungsten wets readily with mercury whilechromium doestnotjthe advantages of a mercury to mercury contact areretained without affecting the sensitivity; l

The Iassembly of a mercuryl container l19 is illustrated in Fig. 3. Acentrallyapertured circular plate 20 is inserted Vin the base 21 sothatthere is aslight clearance between the plateand the ba'se. A portion ofthe plate 20 is cut and bent over to form an annular member 2.2',`

which stabilizes the mercury` surface at the center of the containerwhere the the contact pin may be quite liberal but should be smallenough toprevent any excess mercury from escaping from the container. Y

Theelements of the mercury container 19 are made of a material that willnot amalgam-ate with mercury and are vplated on one side with platinumor other mercury w'ettable substance. `It isof no particular concernwhether the container material is magnetic or non-magnetic. However, inembodyingthe inventionfin specific switch designs there may beadvantages gained in using one material or the other. *The location-ofthese wettable surfaces is illustrated in Figs. 4 and"5 and-is of primeimportance. The interior of the base 21, the exterior of the cover 23,the upper surface of the plate 20 and the lower surface of theannular-member 22 are all mercury wettable,v so that the mercury -withinthe container will adhere tothese surfaces. 'When a drop of mercury hitsthe top of the container 19, capillary forces pull it inside, and thesurface tension of the mercury makes it take the shape shown in Figs. 4and 5. l The mercury surface 24 in the center of the container 19 isconiined between the annular member 22 and the plate 20, so that it isquite stable and its position can be controlled within narrow limits.'The level of the surface 24y would also change very little withV anychange in the volume of the mercury pool 25 inside the container,because of the confining nature of thei'mercury wettable surfaces on theannular member 22 andthe plate 20. Besides forming the mercury surface24,"the annular member `22 provides a small gap through which a portionof the mercury must go when hit by the contact pin 17. Because of thenatural adhesion of the mercury to the wettable surfaces, a mechanicalresistance, or energy loss, is introduced in the circuit which damps thecontact pin 17 and hence the armature 15, thereby preventing chatterwhen the switch closes. The mercury pool 25 acts as a reservoir for themercury surface 24, and because of the particular configuration ,of thecontainer 19 itis very diflicult to shake the mercury out,

leither by jarring or even by inversion of the switch. Consequently, theswitch may be mounted for operation in any position. During longcontinuous operation, a certain amount of the mercury may vaporizeinside the envelope 11. By plating the upper surface' of the cover 23with a mercury Wettable material, the vaporized mercury wil-1 condenseon this surface, and capillary lforces will cause it to return to theinterior of the container 19 through the passageway between the exteriorof the cover 23 and the interior of the base 21.

Referring again vto Fig. l, the mercury container 19 is supported by aVthin non-magnetic plate 26 which is attached to the electrode 13. Theother end of the plate supports a magnetic wire 27, so that a.non-magnetic gap is provided between the wire and the electrode. Thegap is partly filled by the mercury container 19, thereby completing themagnetic circuit. v

Other details will be understood 'om the following description of themode of operation of the device.

. When a magnetic field is applied tothe switch of Fig. l, such as by anenergizing winding 56 enclosing all or part of the envelope 11, there isa repulsive force between the electrode 12 and the armature 15. At thesame time, thereis a force of attractionfbetween the armature 15l andthe wire 27. By making the mercury container 19 `of magnetic materialand placing it in close .y proximity to the end of the electrodev 13,'so that there the curved ux pattern will provide an additional`attractive Iforce that will practically double the sensitivity.However, this is not 'essential for successful operation of the switch.The combined forces result in a force which is roughly linear withthetravel of the contact pin 17.

As the contact pin 17 makes contact with the mercury surface 24, a smallamount of mercury is forced from underneath the annularv member 22, thusproviding a resistive force that will eliminate chatterfon contactmakes, as previously described. 'I'he pin 17 andthe mercury container 19are correlated to provide a small and constant gap therebetween, therebyminimizing the peak voltage induced in the circuit. Because of thewetting characteristics of the annular member Z2, the natural resistanceof the mercury will prevent the pin 17 from striking the container base21, except when a large magnetic force is applied. 'I'his mechanicalcontact may be presented entirely by reducing theV cross sectional areaof the magnetic components until they become magnetically saturated,after which time the amount of external magnetic force applied will havelittle effect on the distance traveled by the contact pin 17.

When the magnetizing current is removed, the natural resiliency of thearmature will move the contact pin 17 out of engagement with the mercurysurface 24, thus opening the circuit. As the armature returns to itsnormal position, it strikes the damping spring 16, thereby reducingvibration.

Fig. 6 illustrates another embodiment of the invention wherein adilerent means for damping thev armature 15 has been provided. In thismodiication the various parts of the structure are substantially similarto those previously described with the exception of a flat spring 28,which has been substituted for the damping spring 16 shown in Fig. 1.The ilat spring is attached to an electrode 29, which is similar totheelectrode 12 (Fig. l) except that it does not extendy as far into theen- 'velope 11. In its normal position the armature 15 is in contactwith the llat spring 28, and since the spring 28 is made of a magneticmaterial the sensitivity of the switch is improved. When the armature 15returns to normal after the magnetizing current is removed, any

vibrations are communicated to the at spring 28, so

that they are effectively damped. This type of spring is particularlyuseful in circuits requiring extremely high sensitivity and freedom fromchatter.

Another embodiment of the invention is shown in Fig.V

7. The basic structure is retained except for the means used for dampingthe vibrations of the armature 15. Attached to the wire electrode 30 isa supporting member 31 to which the armature 15 is fastened. A iine wirecoil 32 is wrapped around the electrode 30 and is secured thereto ateach end by means of a spot Weld or other known method of attachment. Asthe armature 15 returns to normal, it strikes the coil 32 so that thevibrational energy is dissipated and damping is attained. The electrode33 is made tubular in shape to facilitate assembly.

Referring to Fig. 8, there is shown a normally closed mercury switchembodying the features of the invention. Enclosed within the envelope 11are two electrodes 34 and 35. The upper electrode 34v comprises a wireof conductive material with a non-magnetic gap located directly abovethe contact pin 17. The two portions of the electrode 34 are connectedby a non-magnetic plate 36, which has a certain amount of flexibility sothat the vibrations of the armature 37 may be reduced when the switch isopened. The armature is attached to the bottom of the electrode 34 bymeans of the supporting member 38 and is biased in a downward positionso that the contact pin 17 attached to its free end is in engagementwith the mercury in the container 19. The contact pin and the containerare illustrated in -be inserted into the envelope.

39 which is attached to the 'end of the tubular electrode 35, thusmaintaining continuity in the magnetic circuit.

When a magnetizing current is applied to a coil encompassing theenvelope 11 (see Fig. 1), there is a repulsive force between the lowerassembly (the container 19, the.k plate 39zand the electrode 35) and thearmature 37. At the same time, there is an attractive force between thearmature 37 and the two segments of the electrode 34. These forcescombine to raise the armature, thereby `disengaging the contact pin 17from the mercury in the container 19. It will be noted that themagnitude of these forces necessary to actuate the switch is very small,and consequently the device is highly sensitive in operation. When themagnetizing current is removed, the natural resiliency of the armaturev37 returns it to its normal position, thereby causing the contact pin17' to engage with theumercury inthe container 19 to close the circuit.

In Fig. 9 there is shown .a mercury switch embodying the features of theinvention designed to effect transfer between circuits. Three electrodes40, 41 and 4Z are enclosed within the envelope 43, which is filled withan inert gas. One of the electrodes-may be made tubular inshape so thatthe inert gas and the mercury can easily A wire support 44 is attachedlengthwise along the electrode 41 and has two right angleprojections 45'and 46,4 one of which is encompassedby a roller 47 which is free torotate thereon. Attached to the lower portions of the roller 47 and theprojection 45 is a flat vspring 48, which is held in place by spotwelding or other suitable means. An armature 49 is fastened to theroller 47 and pivots about the projection 46. It is so positioned thatin its actuated position (left end moved upward) the right end thereofrests against the flat spring 48. The resiliency of the spring 48therebyprovides ani-effective method of armature damping that willreduce chatter. The positioning of the above-described means forsupporting the armature 49 is illustrated in detail in Fig. l0.

Attached to opposite sides of the left end of the armature 49 are twoaxially aligned contact pins 50 and 51. These pins are identical withthose illustrated in Figs. 4 and 5 and conform to the previousdescription. A mercury container 52 is supported by amagnetic plate 54,which should not extend beyond the tip of the armature 49 in order toinsure maximum sensitivity and operating efficiency.y Otherwise, therewould be small attractive forces built up between the left end of theplate 54 and the armature 49 which would tend to hamper proper operationof the switch. `A mercury container 53 is supported by a non-magneticplate 55, which is secured -to the electrode 40 in `such a manner thatthe outer segment 40 of the electrode is supported thereby. The mercurycontainers 52 and 53 are -positioned so that they may be engaged by thecontact pins 50 and 51, respectively, and are of a constructionidentical with that hereinbefore described. The various components ofthe abovedescribed transfer switch are held together by spot welding orother suitable means of attachment.

In its normal position (as shown) the armature 49 is positioned on theroller 47 so that the contact pin 50 is in engagement With the mercuryin the container 52,

The mercury container is supported by a magnetic plate thus forming acontinuous current carrying path from the electrode 41 to the electrode42. When an external magnetizing current is applied to a coilencompassing the electrode 43 (see Fig. 1), there is a repulsive forcebetween the armature `49 and the magnetic plate 54. Simultaneously,there is a Iforce of attraction between the armature 49 and the twosegments of the electrode 40. These combined forces cause the armatureto move to ward the mercury container 53, disengaging the contact pin 50from the mercury container 52 and engaging the contact pin 51 with themercury container 53. Hence the circuit is transferred from theelectrode 42 to the electrode 40, forming a continuous current carryingpath When the magnetizing current is released, the torsional force ofthe flat spring 48 acting on the roller 47 causes the armature 49 torotate in a counterclockwise direction about the projection 46. Hence,the contact pin 51 disengages from the mercury container 53 and thecontact pin 50 comes into contact with the mercury container 52, therebyreturning the switch to its normal position.

It is apparent that the various modifications of the component parts ofthe switch are, in many instances, interchangeable with each other, andthat certain of the mechanical details shown may be modied withoutdeparting from the scope and spirit of the invention as dened in theappended claims.

What is claimed is:

1. A switch comprising a pair of magnetic members, one of said membershaving a non-magnetic strip, a contact mounted on said non-magneticstrip, a magnetic con tact arm extending between said members having oneend in proximity to said contact, and magnetizing means disposed incooperative relationship to said members for moving said contact arminto or out of engagement with said contact.

2. A switch comprising a pair of magnetic members having juxtaposedsubstantially parallel portions, a magnetic contact arm extendingbetween said members and having one end free and the other end iixed toone of said members, a contact mounted by the other of said memberslopposite the free end of said contact arm, and means for magnetizingsaid members oppositely relative to said contact arm and in thedirection to move said contact arm into or out of engagement with saidcontact.

3. A switch comprising a pair of magnetic members having juxtaposedsubstantially parallel portions, a magnetic armature extending betweensaid members, said armature having one end free and the other end iixedto one of said members, a iirst contact carried by said armature, asecond contact mounted'by the other of said members opposite said rstcontact, and means for magnetizing said members oppositely relative tosaid armature and in the direction to move said first contact into orout of engagement with said second contact.

4. A switch comprising a pair of magnetic members having spacedsubstantially parallel portionsfoneof said members having a non-magneticstrip, a container mounted upon said strip and having an aperturetherein, a body of mercury in said container, a magnetic contact armextending between said members having one end in proximity to saidaperture, and a signal coil encircling said members. i

5. A switch comprising a pair of magnetic members having spacedsubstantially parallel portions, one of said members having anon-magnetic strip, .a container mounted upon said strip and having anaperture therein, a body of mercury in said container, a magneticarmature between said members, said armature having one end fixed tosaid other member and its other end in proximity to said aperture, acontact mounted on said armature 'and aligned with said aperture, andmeans for magnetizing said members oppositely relative to said armatureand in the direction to move said contact into or out of engage mentwith said mercury.

6. In a switch, a pair of magnetic rods having juxtaposed substantiallyparallel portions, a non-magnetic strip mounted by one of said rods andextending from one end thereof, a magnetic member extending from the endof said strip remote from said one rod, the other of said rods having anend portion opposite said member, a contact mounted on said strip,a'rnagnetic contact arm between said rods having one end in proximity tosaid contact and means for magnetizing said rods oppositely relative tosaid contact arm and in the direction to move said contact arm into orout of engagement with said contact.

7. In a switch, a pair of spaced magnetic rods having juxtaposedsubstantially parallel portions, a non-magnetic strip mounted by Yone ofsaid rods and extending from one end thereof, a magnetic memberextending from the end of said strip remote from said one rod, the otherof said rods having an end portion opposite said member, a contactmounted on said str-ip, a rnagnetic contact arm between said rods, saidcontact arm having one end fixed to said other rod and its other end inproximity to said contact, and signal coil means disposed about saidrods.

S. A switch comprising a pair of magnetic rods having juxtaposedsubstantially parallel portions, a non-magnetic strip mounted by one ofsaid rods and extending from oneend thereof, a magnetic member extendingfrom the end of said strip remote from said one rod, the other of saidrods havingl an end portion opposite said member, a first contactmounted on said strip, a magnetic armature between said rods, saidarmature having one end fixed to said other rod and its other end inproximity to said rst contact, a second contact mounted on said armatureand aligned with said rst Contact, and signal coil means disposed aboutsaid rods.

9. A switch comprising a pair of spaced magnetic rods having juxtaposedsubstantially parallel portions, a non-magnetic strip mounted by one ofsaid rods and extending from one end thereof, a magnetic memberextending from the end of said strip remote from said one rod, the otherof said rods having an end portion opposite said member, a containermounted upon said strip and having an aperture therein, a body ofmercury in said container, a magnetic armaturerbetween said rods,

said armature having one end xed to said other rod and its other end inproximity to said aperture, a contact mounted on said armature andaligned with said aperture, and signal coil means disposed about saidrods.

References Cited in the tile of this patent UNITED STATES PATENTS2,797,329 George June 25, 1957

